Designing for the Life Span Segment 3
Designing for the Life Span Segment 3 
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[D]
Normal Age Changes: Determining the Onset of Sensory Modality Losses Related to AgeSensory Modality Normal Change Age of OnsetNote: Every individual experiences age related changes differentially. The onset ages must be seen as generally applicable throughout the entire population. Some individuals will not experience specific losses while others will experience the onset at even earlier ages. By the age of 70, most aging people will have some level of difficulty with hearing and vision. Touch, taste and smell may decline at slower rates and may not be noticeable to individuals within their range of experience to judge.
| Sensory Modality | Normal Change | Age of Onset |
|---|---|---|
| Hearing | selective frequency hearing loss | 40 |
| Vision | color sensitivity and susceptibility to glare | 50 |
| Touch | fine discrimination of textures | 55 |
| Taste | gradual loss of general sensitivity | 55-59 |
| Smell | slight loss of general sensitivity | 70 |
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From a physiological perspective, that aspect of human development marked by loss of capability, has an onset in the middle years. As the chart illustrates, normal hearing changes can begin at age 40. Hearing losses may occur in early years owing to environmental noise pollution. Those losses are being seen with greater frequency.
Normal age related hearing loss is termed "presbycusis" and is a selective frequency sensitivity hearing loss. Vision changes are multiple - including acuity and adaptation. However, the vision changes less well understood are changes in color sensitivity and susceptibility to glare with an onset in the 50s. Touch, taste and smell suffer less reduction in sensitivity, but some losses do occur nonetheless.
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